Currently, the treatment of diabetes, both type 1 diabetes and type 2 diabetes, relies to an increasing extent on the so-called intensive insulin treatment. According to this regimen, the patients are treated with multiple daily insulin injections comprising one or two daily injections of long acting insulin to cover the basal insulin requirement supplemented by bolus injections of a rapid acting insulin to cover the insulin requirement related to meals.
Long acting insulin compositions are well known in the art. Thus, one main type of long acting insulin compositions comprises injectable aqueous suspensions of insulin crystals or amorphous insulin. In these compositions, the insulin compounds utilized typically are protamine insulin, zinc insulin or protamine zinc insulin.
Certain drawbacks are associated with the use of insulin suspensions. Thus, in order to secure an accurate dosing, the insulin particles must be suspended homogeneously by gentle shaking before a defined volume of the suspension is withdrawn from a vial or expelled from a cartridge. Also, for the storage of insulin suspensions, the temperature must be kept within more narrow limits than for insulin solutions in order to avoid lump formation or coagulation.
Another type of long acting insulin compositions are solutions having a pH value below physiological pH from which the insulin will precipitate because of the rise in the pH value when the solution is injected. A drawback with these solutions is that the particle size distribution of the precipitate formed in the tissue on injection, and thus the release profile of the medication, depends on the blood flow at the injection site and other parameters in a somewhat unpredictable manner. A further drawback is that the solid particles of the insulin may act as a local irritant causing inflammation of the tissue at the site of injection.
Human insulin has three primary amino groups: the N-terminal group of the A-chain and of the B-chain and the ε-amino group of LysB29. Several insulin derivatives which are substituted in one or more of these groups are known in the prior art.
WO 95/07931 (Novo Nordisk A/S) discloses human insulin derivatives wherein the ε-amino group of LysB29 has a lipophilic substituent. These insulin derivatives have a prolonged profile of action and are soluble at physiological pH values.
International patent application WO 96/29344 concerns an insulin derivative, where a lipofilic sidechain is attached to the N-terminal amino group of B-chain or a Lys residue at position B26-B29 of the parent insulin molecule.
WO 97/31022 discloses insulin derivatives wherein the α-amino group of N-terminal group of the B-chain and/or the ε-amino group of Lys at position B28, B29 or B30 has a substituent of the formula —CO—W—COOH where W is be a long chain hydrocarbon group having from 12 to 22 carbon atoms. These insulin derivatives have a prolonged profile of action and are soluble at physiological pH values.
Another insulin derivative is disclosed in international patent application. The application patent application WO 2005/012347 describes an insulin derivative having a side chain attached to either the α-amino group of the N-terminal amino acid residue of the B-chain or to the ε-amino acid of a Lys residue present in the B-chain of the parent insulin.
Unfortunately, many diabetics are unwilling to undertake intensive therapy due to the discomfort associated with the many injections required to maintain close control of glucose levels. This type of therapy can be both psychologically and physically painful. Upon oral administration, insulin is rapidly degraded in the gastro intestinal tract and is not absorbed into the blood stream. Therefore, many investigators have studied alternate routes for administering insulin, such as oral, rectal, transdermal, and nasal routes. Thus far, however, these routes of administration have not resulted in effective insulin absorption.
Efficient pulmonary delivery of a protein is dependent on the ability to deliver the protein to the deep lung alveolar epithelium. Proteins that are deposited in the upper airway epithelium are not absorbed to a significant extent. This is due to the overlying mucus which is approximately 30-40 μm thick and acts as a barrier to absorption. In addition, proteins deposited on this epithelium are cleared by mucociliary transport up the airways and then eliminated via the gastrointestinal tract. This mechanism also contributes substantially to the low absorption of some protein particles. The extent to which proteins are not absorbed and instead eliminated by these routes depends on their solubility, their size, as well as other less understood characteristics.
There is still a need for insulins having a more prolonged profile of action than the insulin derivatives known up till now and which at the same time are soluble at physiological pH values and have a potency which is comparable to that of human insulin. Furthermore, there is need for further insulin formulations which are well suited for pulmonary application.
The present invention addresses and alleviates the problems of the prior art.